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Posted by on Jul 23, 2014 in News

Raspberry Pi HATs revealed. “It’s plug and play for Pi,” says Model B+ designer

Raspberry Pi HATs revealed. “It’s plug and play for Pi,” says Model B+ designer

UPDATE: RaspberryPi Foundation officially announces Hardware Attached on Top (HAT). It’s the name for the new standard for Raspberry Pi Model B+ add-on boards. The Foundation’s Director of Hardware, James Adams, explains all.

The Rapsberry Pi Foundation has officially announced HATs.

Original Story:

“Arduino has Shields, Beagleboard has Capes and soon the Raspberry Pi will have HATs,” says James Adams, the designer of the Raspberry Pi Model B+.

The news – part of a forthcoming interview with the Director of Hardware at the Raspberry Pi Foundation about the making of the Model B+ – means we’ll soon be seeing a new generation of add-on boards for the Raspberry Pi.

“The two GPIO pins that sit just after the 26th pin on the Model B+ are going to provide plug and play capability for a new kind of add-on board for the Raspberry Pi Model B+,” says Adams. “I’m working on the specifications and documentation right now.”

“It’s actually a three letter acronym standing for Hardware Attached on Top, because we thought it sounded cute,” he continued. “We actually designed the Model B+ specifically with add-on boards in mind.”

It’s likely we’ll start hearing about new add-on boards in the fields of robotics for motor control, Input and Output expanders and Liquid Crystal Display boards announced very soon.


Adams went on to explain that the new layout makes it easy to sit a HAT add-on board on top of the Pi. “If you look at the board you can see where the big [USB and Ethernet] connectors are on one side, but all the other connectors are low profile so you can have a nice square-ish board sitting on top of the GPIO pins with the four mounting holes in the corner allowing you to easily attach it.”

“Those specific pins are designed for an EPROM (Erasable Programmable Read Only Memory) to sit on the plug-in board. When the Pi turns on it will interrogate those pins looking for the EPROM. If it finds it, it will download the data inside and that data will tell it how to set the GPIO pins up, what devices are attached and therefore what drivers to load into Linux,” says Adams.

“The end user will buy a board that supports a feature, plug it it, power up the Pi and bang… it recognises the board and maybe it will even load up software and put icons on your desktop. That’s the end goal and we’re working really hard to change the software to support it.”

This sort of automatic way of telling Linux what hardware is attached is actually already a standard in Linux, but Adams and the Foundation are working hard to make it work nicely on the Raspberry Pi Model B+ and also on the Raspberry Pi Compute Module.

The Foundation seems confident it will be a massive boon for all Rapsberry Pi users, but it’s expected to be particularly popular within the realm of education, where plug and play compatibility will likely help lower the technical hurdles faced by teachers. “The Model B+ is definitely the Raspberry Pi for schools,” concluded Adams.

Raspberry Pi HATs github

The specs and documentation Adams mentioned earlier has recently been uploaded to Github, which means HAT makers have everything they need to start creating new Model B+ add-on boards or tweaking current boards to be HAT compatible.